Ceratopsia

Ornithischia

Cerapoda

Marginocephalia

Ceratopsia

What this amounts to is that Ceratopsia were "Bird-hipped" (Ornithischia, as opposed to Lizard-hippedSaurischia),
with thick enamel on their teeth (Cerapoda), and Frilly Heads
(Marginocephalia). The frills on their heads might have
served as heat radiators; in the case of later Tricerotops they were
most likely used
for defense. Their beak and rows of grinding teeth suggests a diet of
vegetation. The teeth would wear unevenly, creating serrated edges for
shearing through plant material.

Early versions of this group, such as
Psittacosauridae were smaller and walked on two legs; their remains
are found in Asia. Later versions, such as the Triceratops, were
large and quadrepedal, and can be found in North America.